Method and apparatus for performing phase detection and timing recovery for a vestigial sideband receiver

1. A timing recovery apparatus comprising: a frequency shifter; a polyphase interpolation filter connected to the frequency shifter; a bandedge prefilter connected to the polyphase interpolation filter; a phase detector, connected to the bandedge filter, having a fourth order nonlinearity; a loop filter connected to the phase detector; and a numerically controlled oscillator connected to the loop filter and connected to the polyphase interpolation filter.

2. The apparatus of claim 1 wherein the output of the phase detector is real valued.

3. The timing recovery apparatus of claim 1 wherein the fourth order nonlinearity is defined by v ( t ) g ( t ) g * ( t ) y ( t ) sgn ( Re v ( t ) ) Im v ( t ) where y(t) is an output of the phase detector, g(t) is a complex valued prefilter output for an upper bandedge, g(t) is a prefilter output for a lower bandedge.

4. The timing recovery apparatus of claim 1 wherein the bandedge prefilter produces a lower complex bandedge signal and an upper complex bandedge signal and said phase detector comprises: a complex conjugate block for producing a complex conjugate of the lower complex bandedge signal; a complex multiplier for multiplying the complex conjugate of the lower complex bandedge signal with the upper complex bandedge signal producing a multiplied signal; an imaginary extractor for extracting the imaginary component of the multiplied signal; a real extractor for extracting a real component of the multiplied signal; a signum function block for applying a signum function to the real component of the multiplied signal; and a real multiplier for multiplying an output of signum function block with the imaginary component of the multiplied signal to produce a phase error signal.

5. A high definition television comprising: a tuner for selecting a vestigial sideband (VSB) signal from a plurality of VSB signals; an analog-to-digital (A/D) converter for digitizing the selected VSB signal; a timing recovery circuit for processing the digitized VSB signal to extract in-phase and quadrature phase components of the VSB signal, where said timing recovery circuit uses a high order nonlinearity to detect the phase of the VSB signal and further comprises: a frequency shifter; a polyphase interpolation filter connected to the frequency shifter; a bandedge prefilter connected to the polyphase interpolation filter; a phase detector, connected to the bandedge filter having a fourth order nonlinearity;. a loop filter connected to the phase detector; and a numerically controlled oscillator connected to the loop filter; and a decoder for extracting data from the in-phase component of the VSB signal.

6. The high definition television of claim 5 wherein the output of the phase detector is real valued.

7. The high definition television of claim 5 wherein the phase detector uses a high order nonlinearity defined by v ( t ) g ( t ) g * ( t ) y ( t ) sgn ( Re v ( t ) ) Im v ( t ) where y(t) is an output of the phase detector, g(t) is a complex valued prefilter output for an upper bandedge, g(t) is a prefilter output for a lower bandedge.

8. The high definition television of claim 7 wherein the bandedge prefilter produces a lower complex bandedge signal and an upper complex bandedge signal and said phase detector comprises: a complex conjugate block for producing a complex conjugate of the lower complex bandedge signal; a complex multiplier for multiplying the complex conjugate of the lower complex bandedge signal with the upper complex bandedge signal producing a multiplied signal; an imaginary extractor for extracting the imaginary component of the multiplied signal; a real extractor for extracting a real component of the multiplied signal; a signum function block for applying a signum function to the real component of the multiplied signal; and a real multiplier for multiplying an output of signum function block with the imaginary component of the multiplied signal to produce a phase error signal.